Optical and Dielectric Properties of BaF₂:(Er,Yb) Co-Doped Crystal

A BaF₂ single crystal co-doped with Er³⁺ and Yb³⁺ was grown by the vertical Bridgman technique and investigated for its optical and dielectric properties. Judd-Ofelt analysis yielded intensity parameters Ω₂ = 0.59, Ω₄ = 0.38, and Ω₆ = 0.27 (×10^-20 cm²), with a quality factor χ = 1.41, indicating strong radiative transitions. Under UV and near-UV excitation, emissions at 321, 405, 518, and 536 nm were observed, with radiative lifetimes ranging from 1.1 to 3.4 ms. A single dielectric relaxation process was identified, with activation energy of 0.58 eV and associated with trigonal NNN dipoles. The NNN dipole concentration was estimated at ~2.5 × 10¹⁸ cm^-3. These results support the suitability of Er³⁺,Yb³⁺ co-doped BaF₂ crystals for luminescent and dielectric applications in advanced photonic materials.